One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(5,6,9,11)(7,12,8,10)(13,14,17,19)(15,23,26,20)(16,27,24,21)(18,22,25,28)(5,6)(7,10)(8,12)(9,11)(14,19)(15,24)(16,26)(18,25)(20,21)(23,27) involution — undirected(2,4)(13,15,25,16,17,26,18,24)(14,20,28,21,19,23,22,27)(5,7,9,8)(6,10,11,12)(14,19)(20,23)(21,27)(22,28)(5,8,9,7)(6,10,11,12)(13,16,18,15,17,24,25,26)(14,21,22,20,19,27,28,23)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.